Method for press forming glass sheets

Abstract

A method, press station ( 12 ), and system ( 10 ) for forming glass sheets that are initially formed with an upwardly concave curved shape with end portions ( 86 ) and an intermediate portion ( 88 ) having straight line elements that are subsequently formed with curved shapes to provide curvature along transverse directions. The forming is performed by initially providing curvature to the straight line elements of the glass sheet end portions while the intermediate portion ( 88 ) still has the straight line elements. The glass sheet intermediate portion is subsequently formed to provide curvature to its straight line elements so the glass sheet has curvature in transverse directions.

What is claimed is: 
     
       1. A method for forming glass sheets comprising:
 initially forming a heated flat glass sheet to an upwardly concave curved shape with upper end portions and a lower intermediate portion extending between the upper end portions, with the upper end portions and intermediate portion having shapes with straight line elements, and with the glass sheet curved transversely to the straight line elements; 
 locating the initially formed glass sheet below an upper mold having a downwardly facing surface with downwardly convex curvature along transverse directions; 
 moving the end portions of the glass sheet upwardly relative to the intermediate portion to initially contact the end portions of the glass sheet with the downwardly facing surface of the upper mold to form the straight line elements of the end portions with curvature while the intermediate portion of the glass sheet still has straight line elements without any significant curvature; and 
 thereafter moving the intermediate portion of the glass sheet upwardly relative to its end portions to contact the intermediate portion of the glass sheet with the downwardly facing surface of the upper mold to also form the straight line elements of the intermediate portion with curvature so the entire glass sheet is curved along transverse directions. 
 
     
     
       2. A method for forming glass sheets as in  claim 1  wherein the glass sheet is initially formed with a cylindrical shape that has the straight line elements. 
     
     
       3. A method for forming glass sheets as in  claim 1  wherein the glass sheet is initially formed with a conical shape that has the straight line elements. 
     
     
       4. A method for forming glass sheets as in  claim 1  wherein the straight line elements of the end portions of the glass sheet are formed with curvature against the upper mold before the intermediate portion contacts the upper mold. 
     
     
       5. A method for forming glass sheets as in  claim 1  wherein the end portions of the glass sheet are each initially pressed against the downwardly facing surface of the upper mold with a predetermined force that is subsequently reduced to facilitate movement of the end portions of the glass sheet along the downwardly facing surface of the upper mold as the intermediate portion of the glass sheet continues to move for forming against the downwardly facing surface of the upper mold. 
     
     
       6. A method for forming glass sheets as in  claim 1  wherein the heated flat glass sheet is initially formed within a heating chamber on a conveyor by inclined rolls of progressively increasing inclination along a direction of conveyance and is then conveyed out of the heating chamber to a press station at which the upper mold is located. 
     
     
       7. A method for forming glass sheets as in  claim 6  wherein the initially formed glass sheet is lifted upwardly off of the conveyor in the press station by a lower ring that is moved upwardly from below the glass sheet and has: (a) end portions spaced laterally from each other relative to the direction of conveyance with upwardly concave curved shapes along the direction of conveyance, and (b) intermediate portions spaced from each other along the direction of conveyance with upwardly concave curved shapes extending transversely to the direction of conveyance between the end portions of the lower ring, after the lower ring lifts the glass sheet upwardly off the conveyor the end portions of the lower ring being moved upwardly relative to the intermediate portions of the lower ring to contact and form the end portions of the glass sheet against the downwardly facing surface of the upper mold while the intermediate portion of the glass sheet is still located below the downwardly facing surface of the upper mold, and after the end portions of the lower ring form the end portions of the glass sheet against the downwardly facing surface of the upper mold the intermediate portions of the lower ring being moved upwardly to contact and form the intermediate portion of the glass sheet with the downwardly facing surface of the upper mold to complete the press forming. 
     
     
       8. A method for forming glass sheets as in  claim 7  wherein the end portions of the glass sheet are each initially pressed against the downwardly facing surface of the upper mold by the end portions of the lower ring with a predetermined force that is subsequently reduced to facilitate movement of the end portions of the glass sheet along the downwardly facing surface of the upper mold as the intermediate portion of the glass sheet continues to be moved upwardly by the intermediate portions of the lower ring into contact for forming against the downwardly facing surface of the upper mold. 
     
     
       9. A method for forming glass sheets comprising:
 initially forming a heated flat glass sheet within a heating chamber on a conveyor by inclined rolls of progressively increasing inclination along a direction of conveyance so as to have an upwardly concave curved shape with upper end portions and a lower intermediate portion extending between the end portions, with the upper end portions and the intermediate portion having shapes with straight line elements, and with the glass sheet curved transversely to the straight line elements; 
 conveying the initially formed glass sheet on the conveyor along the direction of conveyance into a press station above a lower ring that has: (a) end portions spaced laterally from each other relative to the direction of conveyance and extending along the direction of conveyance with respective upwardly concave curved shapes, and (b) intermediate portions spaced from each other along the direction of conveyance and extending transversely to the direction of conveyance between the end portions of the lower ring with respective upwardly concave curved shapes; 
 moving the lower ring upwardly to lift the initially formed glass sheet upwardly off of the conveyor toward an upper mold having a downwardly facing surface with downwardly convex curvatures both along and transverse to the direction of conveyance and complementary to the upwardly curved shapes of the end portions and the intermediate portions of the lower ring; 
 after the initially formed glass sheet is lifted upwardly off the conveyor, moving the end portions of the lower ring upwardly relative to the intermediate portions of the lower ring to initially contact the end portions of the glass sheet with the downwardly facing surface of the upper mold to form the straight line elements of the end portions with curvature while the intermediate portion of the glass sheet is below the downwardly facing surface of the upper mold; and 
 thereafter moving the intermediate portions of the lower ring upwardly relative to its end portions to contact and form the intermediate portion of the glass sheet against the downwardly facing surface of the upper mold to also form the straight line elements of the intermediate portion of the glass sheet with curvature so the entire glass sheet has curvature in transverse directions.